Generally, in a fluid transfer circuit for a motor vehicle, in order to connect a flexible or rigid hose that has a male end-piece that is lockable via a collar which it has, it is known to use a connection device which incorporates a female end-piece which is provided by welding or clip-fitting with a female connector which receives this male end-piece, an annular seal which is pressed against the male end-piece after the latter has been fitted in the female connector, and a locking pin which is inserted through this female connector in order to block the end-piece therein in a pushed-in and locked position. Mention may, for example, be made of document FR-B1-2 891 889 for the description of such a lockable connection device and the documents FR-B1-2 855 590 and WO-A1-2006/099933 which describe various metal locking pins which can be used in such a device.
A major disadvantage of these known connection devices is that they do not have sufficient mechanical grip with respect to end-pieces which have a collar of low radial height, which may result in the disconnection of the device by the pin becoming disengaged with respect to the male end-piece.
Another disadvantage of these existing devices having a metal pin is that they do not facilitate the fitting of the pin in contact with the male end-piece.